/*
 * LensKit, an open-source toolkit for recommender systems.
 * Copyright 2014-2017 LensKit contributors (see CONTRIBUTORS.md)
 * Copyright 2010-2014 Regents of the University of Minnesota
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
package org.lenskit.knn.item.model;

import com.google.common.base.MoreObjects;
import org.lenskit.knn.item.ItemSimilarityThreshold;
import org.lenskit.knn.item.ModelSize;
import org.grouplens.lenskit.transform.threshold.Threshold;
import org.grouplens.lenskit.transform.truncate.ThresholdTruncator;
import org.grouplens.lenskit.transform.truncate.TopNTruncator;
import org.grouplens.lenskit.transform.truncate.VectorTruncator;

import javax.inject.Inject;
import javax.inject.Provider;

/**
 * Configure a vector truncator using the standard item-item model build logic.
 *
 * @since 2.1
 * @author <a href="http://www.grouplens.org">GroupLens Research</a>
 */
public class StandardVectorTruncatorProvider implements Provider<VectorTruncator> {
    private final Threshold threshold;
    private final int modelSize;

    /**
     * Construct a new vector truncator provider.
     * @param thresh A threshold for filtering item similarities.
     * @param msize The maximum number of neighbors to retain for each item.
     */
    @Inject
    public StandardVectorTruncatorProvider(@ItemSimilarityThreshold Threshold thresh,
                                           @ModelSize int msize) {
        threshold = thresh;
        modelSize = msize;
    }

    @Override
    public VectorTruncator get() {
        if (modelSize > 0) {
            return new TopNTruncator(modelSize, threshold);
        } else {
            return new ThresholdTruncator(threshold);
        }
    }

    @Override
    public String toString() {
        return MoreObjects.toStringHelper(StandardVectorTruncatorProvider.class)
                          .add("modelSize", modelSize)
                          .add("threshold", threshold)
                          .toString();
    }
}
